In cable television signal distribution systems, many separate radio frequency (RF) television channels are simultaneously transmitted over a transmission line, and a required bandwidth thereof may extend from as low as about 40 MHz to as high as about 1 GHz. Presently, cable television distribution systems conventionally employ coaxial cable as the transmission line for the RF spectra. Due to the significant signal losses inherent with coaxial cable transmission lines, repeater amplifiers must usually be provided at closely spaced distances, such as at every half mile along the extent of the network. These repeaters are expensive, require a constant power supply, introduce cumulative distortion, and must be maintained in order to provide continuous cable service to subscribers.
Optical communications lasers, such as laser diodes and distributed feedback (“DFB”) lasers, exhibit significant amounts of intermodulation distortion, particularly composite second order (CSO) distortion products, i.e. distortion products of the type 2f1, 2f2, f2−f1, and f2+f1. Predistortion techniques have been proposed as one method for improving distortion levels at the laser output.